US8405757B2ActiveUtilityA1

Imaging device

Assignee: KUBOTA YOJIPriority: Oct 29, 2010Filed: Oct 27, 2011Granted: Mar 26, 2013

Est. expiryOct 29, 2030(~4.3 yrs left)· nominal 20-yr term from priority

Inventors:Yoji Kubota Kenichi Kubota Hitoshi Hirano

G02B 5/04G02B 17/0852

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Claims

Abstract

An imaging device includes a light source; a prism having an imaging surface to be contacted with an object; and an image-forming optical system that forms an image of the object. The image-forming optical system includes a front lens group having a first optical axis tilted relative to the imaging surface; an image plane tilted from a surface perpendicular to the first optical axis of the front lens group; and a rear lens group having a second optical axis shifted in parallel to the first optical axis of the front lens group. The image-forming optical system is arranged to satisfy the following conditional expression: |Aim|/(90°−Ain)<0.5 Where Ain is an acute angle between the imaging surface and the first optical axis, and Aim is an angle between the image plane and a surface perpendicular to the first optical axis.

Claims

exact text as granted — not AI-modified

What is claimed is: 
     
       1. An imaging device comprising:
 a light source that emits light; 
 a prism having an imaging surface to be contacted with an object having a pattern formed thereon so that the light from the light source totally reflects on the imaging surface; and 
 an image-forming optical system that forms an image of the object, 
 wherein said image-forming optical system comprises: 
 a front lens group having a first optical axis tilted relative to the imaging surface, said front lens group having positive refractive power; 
 an image plane tilted from a surface perpendicular to the first optical axis of the front lens group; and 
 a rear lens group disposed on a side of the image plane relative to the front lens group and having a second optical axis shifted in parallel to the first optical axis of the front lens group, said rear lens group having negative refractive power, and 
 said image-forming optical system is arranged to satisfy the following conditional expression:
   | Aim |/(90 °−Ain )&lt;0.5 
 
 
       where Ain is an acute angle between the imaging surface and the first optical axis of the front lens group, and Aim is an angle between the image plane and a surface perpendicular to the first optical axis of the front lens group. 
     
     
       2. The imaging device according to  claim 1 , further comprising at least one mirror arranged to reflect the light from the prism so that the light enters the front lens group. 
     
     
       3. The imaging device according to  claim 1 , wherein said front lens group includes a first lens formed in a meniscus shape and having a convex surface that directs toward the object, said first lens having positive refractive power, and a second lens formed in a meniscus shape and having a concave surface that directs toward the object, said second lens having positive refractive power. 
     
     
       4. The imaging device according to  claim 1 , wherein said rear lens group includes a third lens formed in a meniscus shape and having a convex surface that directs toward the object, said third lens having negative refractive power, and a fourth lens formed in a meniscus shape and having a convex surface that directs toward the object, said fourth lens having negative refractive power. 
     
     
       5. The imaging device according to  claim 1 , wherein said image-forming optical system is arranged to satisfy the following expression:
   −0.5 &lt;DC/Fr&lt; 0
 
 
       where DC is a shifted amount between the first optical axis and the second optical axis, and Fr is a focal length of the rear lens group. 
     
     
       6. The imaging device according to  claim 1 , wherein said image-forming optical system is arranged to satisfy the following expression:
   −1.5 &lt;Ff/Fr&lt;− 0.5
 
 
       where Ff is a focal length of the front lens group and Fr is a focal length of the rear lens group. 
     
     
       7. An imaging device that captures an image of an imaging surface in an oblique direction, comprising:
 a front lens group having a first optical axis tilted relative to the imaging surface, said front lens group having positive refractive power; 
 an image plane tilted from a surface perpendicular to the first optical axis of the front lens group; and 
 a rear lens group disposed on a side of the image plane relative to the front lens group and having a second optical axis shifted in parallel to the first optical axis of the front lens group, said rear lens group having negative refractive power, and 
 said image-forming optical system is arranged to satisfy the following conditional expression:
   | Aim |/(90 °−Ain )&lt;0.5 
 
 
       where Ain is an acute angle between the imaging surface and the first optical axis of the front lens group, and Aim is an angle between the image plane and a surface perpendicular to the first optical axis of the front lens group. 
     
     
       8. The imaging device according to  claim 7 , wherein said front lens group includes a first lens formed in a meniscus shape and having a convex surface that directs toward an object on the imaging surface, said first lens having positive refractive power, and a second lens formed in a meniscus shape and having a concave surface that directs toward the object, said second lens having positive refractive power. 
     
     
       9. The imaging device according to  claim 7 , wherein said rear lens group includes a third lens formed in a meniscus shape and having a convex surface that directs toward an object on the imaging surface, said third lens having negative refractive power, and a fourth lens formed in a meniscus shape and having a convex surface that directs toward the object, said fourth lens having negative refractive power. 
     
     
       10. The imaging device according to  claim 7 , wherein said image-forming optical system is arranged to satisfy the following expression:
   −0.5 &lt;DC/Fr&lt; 0
 
 
       where DC is a shifted amount between the first optical axis and the second optical axis, and Fr is a focal length of the rear lens group. 
     
     
       11. The imaging device according to  claim 7 , wherein said image-forming optical system is arranged to satisfy the following expression:
   −1.5 &lt;Ff/Fr&lt;− 0.5
 
 
       where Ff is a focal length of the front lens group and Fr is a focal length of the rear lens group.

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